1. Field of the Invention
The present invention is related to an actuator control system of a magnetic storage device, and specifically to an actuator control system that reduces the effects of aliasing inherent in the digital control.
2. Description of Related Art
The performance of an actuator control of a magnetic storage device, such as a hard disk drive (HDD), may be degraded by the aliasing caused by the mechanical resonances of a head suspension. In particular, the mechanical resonances resulting from the head gimbal assembly (HGA) and the actuator may reduce the robustness of a HDD, and furthermore raise the acoustic noise during a high-speed seek operation of a HDD.
One conventional approach to address the effects of such mechanical resonances is presented in the Japan Published Unexamined Patent Application No. 5-166312. According to this publication, a low pass filter (LPF) having a low pole is placed immediately after a digital-to-analog converter (DAC) to reduce the gain in the high frequency region where the resonance is located. Because the LPF also affects characteristics in the low frequency region, the effect of the LPF in the low frequency region is digitally compensated. This actuator control system is often referred to as a hybrid system because it incorporates a combination of analog and digital circuits.
Although the hybrid actuator control system described above has many desirable characteristics, it was designed based on the presumption that the HDD includes hardware with a processor having relatively high arithmetic processing power.
More specifically, this conventional approach was designed to operate with a state estimator to meet the high arithmetic processing power of the DSP. Unfortunately, such a high performance processor often increases the overall cost of a HDD. As a result, many currently available HDDs do not include such a processor; therefore, this conventional hybrid actuator control system approach may not be suitable for many HDDs available today. Accordingly, it is often desirable to simplify the algorithm to the extent that it can be processed by an ordinary microprocessor (MPU) (i.e., a processor without a state estimator) while taking advantage of the desirable characteristics of the hybrid control system.